This invention relates to the production of nematic liquid crystal compositions and to articles or devices including such compositions; and, more particularly, it concerns novel Schiff bases which are useful in producing such nematic liquid crystal compositions and articles, and methods of making the same.
Nematic liquid crystals have heretofore been known to the art, along with light valves, light modulators and display devices utilizing such crystals. These devices are operated by application of an electric field to the composition when it is in the mesomorphic state and when an electric field, or current, of sufficient strength is applied to the liquid crystal composition, the layer of crystals appears to change, for instance in the intensity of transmitted light, in the area of the effective field. The nematic liquid crystal domains align themselves in the applied field. However, some of the prior art nematic liquid crystal compositions have had a mesomorphic range above normal room temperatures and have required heating in order to bring them into a useful state; and others have had a small or narrow temperature range in which they are in the liquid crystal state. Another disadvantage has been the necessity for using a relatively large electrical voltage and current to cause suitable alignment of the nematic liquid crystals in a device.
The above disadvantages are overcome and certain advantages are attained by the present invention as will be shown below.